President Obama is serious this time. No, really. Critics of the president's approach to the Syrian crisis don't understand the many nuances undergirding the president's philosophy of using "smart power" to lead from behind. Forget all those previous signals of how serious he is about taking decisive action to stop the killing. He means it. This time. No, really, he does.

Obama's history of dithering captures the most basic problem confronting the chief executive on Syria: He's promised action over and over again, but in the end has actually offered little more than words. That is why nobody should be surprised that Americans, as well as leaders in Moscow, Beijing, London, Paris, Tehran and Damascus, find it difficult to put much stock in what Obama says now about the Syrian crisis and what he might do in response to Syrian dictator Bashar al-Assad's blatant use of chemical weapons against the Syrian people.

"If you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable."

And who can blame them, considering the timeline put together by the Washington Examiner's Susan Crabtree? That timeline makes clear that Obama has been issuing dire threats, warnings and ultimatums since long before and often since August 2012. That was when Obama first proclaimed that using chemical weapons would "cross a red line. That would change my calculus. That would change my equation."

Among the key points on that 28-point timeline are these:

• After demonstrations calling for Assad's ouster began in March 2011, Obama essentially ordered the dictator in April to stop killing demonstrators and to "change course."

• Then in August 2011, Obama and Turkish Prime Minister Tayyip Erdogan gave Assad an Aug. 27 deadline to stop the violence and start implementing democratic reforms, or else risk joint U.S.-Turkish military action. The deadline passed, Assad continued killing his people and the U.S. did not do as it warned.

• On June 22, 2012, Secretary of Defense Leon Panetta says the U.S. won't give arms or other aid to Syrian rebels.

• On Dec. 3, 2012, Obama warns Assad that "if you make the tragic mistake of using these weapons, there will be consequences and you will be held accountable." Secretary of State Hillary Clinton says the U.S. will take action if chemical weapons are used.

• News reports from the on Pentagon Dec. 7, 2012 describe contingency planning for U.S. military action in Syria.

• Somebody uses chemical weapons March 19, 2013 and Obama says the U.S. is seeking conclusive evidence of who is responsible.

• Obama says on April 30, 2013 that he still doesn't have proof that Assad used chemical weapons.

• Unnamed White House officials say June 14, 2013 that Obama has opted to use military force against Assad.

• August 2013. Amid multiple leaks and background reports from unnamed administration officials, it appeared initially that Obama would order a significant military action. Now, a limited cruise missile attack that does little if anything to stop Assad's murderous attacks on his own people appears more likely.

Who knew that "nuance" actually means "vacillate"?